ANTINEOPLASTIC V LEUKEMOGENIC EPIPODOPHYLLOTOXIN EFFECTS

描述：（申请人的摘要）这项工作的目标是 更好地了解表鬼臼毒素诱导的机制 白血病发生表鬼臼毒素导致治疗相关 染色体11 q23带MLL基因易位的白血病。 目前的证据表明，白血病和致白血病 表鬼臼毒素作用是由于染色体断裂， 通过染色体易位解决的断裂与 白血病表鬼臼毒素母体化合物稳定DNA 拓扑异构酶II-DNA共价中间体，降低DNA拓扑异构酶 II介导的再连接并引起染色体断裂。这些事件 启动凋亡细胞死亡途径， 行动上 表鬼臼毒素代谢成几种化合物， 通过产生脱碱基位点或通过形成 DNA加合物。申请人假设表鬼臼毒素也 因为它的代谢物可能会导致断裂， 易位，以及继发性遗传变化，除了 白血病的发展也可能需要易位。第一 新的数据支持这一假设，即细胞色素基因型 P-450（P450）3A 4可代谢表鬼臼毒素母体药物， 调节风险，而疾病发作的潜伏期表明， 还有一些次要的变化。在目标1中，申请人将克隆MLL 基因组易位断裂点通过柄状变体PCR和检测 白血病前和白血病骨髓连续观察 具有特定易位的细胞的克隆性。在Aim 2中， 申请人将直接比较依托泊苷及其代谢产物的作用 体外DNA拓扑异构酶II切割和MLL基因组上的重新连接 易位断裂点，以及骨中MLL基因内的断裂 骨髓干细胞在目标3中，申请人将测量依托泊苷和 患者血浆和尿液中的潜在致白血病代谢物 接受治疗，同时检查染色体断裂， MLL和接受治疗的受试者中MLL基因易位的出现。 使用cDNA微阵列技术，申请人将评估次级 MLL基因治疗相关白血病的遗传学改变 目的4实验中的易位。成功执行这些 具体目标将提供新的知识的病因，发病机制， 这种治疗并发症的自然史和演变， 推进白血病预防策略的合理设计， 保护这些重要药物的潜在利益。

DESCRIPTION: (Applicant's Abstract) The objective of this work is to better understand the mechanisms of epipodophyllotoxin-induced leukemogenesis. Epipodophyllotoxins result in treatment-related leukemias with translocations of the MLL gene at chromosome band 11q23. Current evidence suggests that both antineoplastic and leukemogenic epipodophyllotoxin effects are due to chromosomal breakage and that breakage resolved by chromosomal translocation is associated with leukemia. Epipodophyllotoxin parent compounds stabilize a DNA topoisomerase II-DNA covalent intermediate, decrease DNA topoisomerase II-mediated religation and cause chromosomal breakage. These events initiate an apoptotic cell death pathway, the desired antineoplastic action. Epipodophyllotoxins are metabolized to several compounds that may also lead to chromosomal breakage by creation of abasic sites or by forming DNA adducts. The applicant hypothesizes that epipodophyllotoxin as well as its metabolites may contribute to the breakage that results in translocations, and that secondary genetic changes, in addition to the translocations may also be required for leukemia to evolve. The first hypothesis is supported by new data that the genotype of cytochrome P-450 (CYP) 3A4, which metabolizes epipodophyllotoxin parent drug, may modulate the risk, while latency to the onset of disease suggests that there are secondary changes. In Aim 1 the applicant will clone MLL genomic translocation breakpoints by panhandle variant PCR and examine serial pre-leukemic and leukemic marrows to observe establishment of clonality by cells with a particular translocation. In Aim 2 the applicant will directly compare effects of etoposide and its metabolites on in vitro DNA topoisomerase II cleavage and religation at MLL genomic translocation breakpoints, and on breakage within the MLL gene in bone marrow stem cells. In Aim 3 the applicant will measure etoposide and potential leukemogenic metabolites in plasma and urine of patients undergoing treatment and concurrently examine chromosomal breakage in MLL and appearance of MLL gene translocations in the treated subjects. Using cDNA microarray technology, the applicant will appraise secondary genetic changes in treatment-related leukemias with MLL gene translocations in experiments of Aim 4. Successful execution of these Specific Aims will provide new knowledge of the etiology, pathogenesis, natural history and evolution of this treatment complication and may advance the rational design of leukemia preventive strategies that preserve the antineoplastic benefit of these important drugs.